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From Rafael Schloming <...@alum.mit.edu>
Subject Re: Python wrapper - SASL and SSL class API
Date Wed, 11 Dec 2013 14:43:59 GMT
On Wed, Dec 11, 2013 at 9:35 AM, Ken Giusti <kgiusti@redhat.com> wrote:

>
> Hi all - just wanted to get some opinions on $Subject:
>
> While I was trying to implement a fix for
> https://issues.apache.org/jira/browse/PROTON-476  I found that the
> lifecycle model for the python SASL and SSL objects differs for the C
> engine.  I think the python wrapper's impl is buggy.
>
> In the C engine, these objects are singletons with respect to their
> associated transport - there can only be one SSL and SASL object associated
> with a given transport.  This is enforce by the C api - the transport
> provides factory classes for these objects.
>
> The python wrapper doesn't enforce this.  For both objects, a "public"
> constructor is supplied (I say "public" because it is exported by the
> wrapper's __all__ list).  This makes it trivial for an application to
> construct multiple instances of SASL/SSL objects that reference the same
> underlying C object.  While this can technically be done safely using
> reference counting, I think it may lead to unanticipated behavior - not to
> mention that it differs from the object model provide by the C engine.
>
> I'd like to fix this by modifying the python wrapper to remove the SSL and
> SASL objects from the __all__ list, and provide factory methods on the
> Transport class for creating instances of these objects.
>
> This would result in a change to the public API.
>

Why exactly do you need to change the API to do this? I would expect there
should be a number of ways to keep it the same, e.g. rename the class and
use a factory function with the same name as the class, or override __new__
if you want to keep the class name the same. Am I missing something?

--Rafael

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